Device for measuring fluid velocity



Nov. 24, 1936. w. v. HUKILL 2,061,941

DEVICE FOR MEASURING FLUID VELOCITY Filed Aug. 22, 1932 J J A AA A A A I V Y V? V V I 2 5 -3 4 /4 l4 Z Allmfill a lNENT R "WITNESSES f' amiig E M Patented Nov. 24, 1936 DEVICE FOR MEASURING FLUID VELOCITY William V. Hukill, Clarendon, Va.

Dedicated to the free use of the Public Application August 22, 1932, Serial No. 629,944

3' Claims. (Cl. 73 -204) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928,

and the invention herein described, it patented,

may be manufactured and used by or for the Government, for governmental purposes, without payment to me of any royalty thereon.

I hereby dedicate the invention herein described, to the free use of the public, to take effect upon the granting of a patent to me.

This invention relates to a device for measuring fluid velocity, including the velocity of air, other gases and liquids.

In cold storage rooms, refrigerator cars and other places it is often desirable to know the rate I of air movement due to natural convection curanemometer which requires the presence of a person for making readings.

The object of the present invention is to measure fluid velocities in the range of ordinary convection currents, and to measure air movement of any velocity at remote or inaccessible places.

Fig. 1 is a diagram of the device, and Figure 2 is a diagram of a modification. In this diagram, I is a wire of a metal or alloy. 3 and 3' are wires of some other metal or alloy having a thermo electric power differing from that of wire I. Wires 3 and 3' are joined to wire I at junctions 5 and 5' to form a thermocouple. The thermocouple is not supported otherwise than by the wires constituting said thermocouple. The other ends of wires 3 and 3' are connected to the terminals of a voltmeter 9. 2 is a heating element of some metal or alloy of appreciable electrical resistance through which electric current from battery 8 may be passed by means of wires 4 and 4' through ammeter l and variable resistance 6. Heating element 2 is closely adjacent to junction 5' and supported thereby, element 2 being wrappedas a coil about junction 5' but is not in electrical contact with it or with wire I or 3', said heating element having been coated with a thin layer of nonconducting oxide by heating in an oxidizing flame. 55 When electric current is passed through heating element 2 it is heated and raises the temperature of junction 5'. The amount of heat generated in heating element 2 may be controlled by means of the variable resistance 6. Junction 5 is not heated by the heating element 2 but remains at or 5 nearly at the temperature of the surrounding medium. The difierence in temperature between the junctions 5 and 5' will cause an electromotive force between the terminals of wires 3 and 3', the magnitude of this electromotive force depending 10 uuon the amount of temperature difference between junctions 5 and 5'. The electromotive force may be measured by means of the voltmeter 9. If

junctions 5 and 5 be placed in an air current, the moving air will cool the heated junction 5', the 15 amount of such cooling depending upon the velocity of the air.

By suitable calibrations, the rate of air movement past the device in any location may be determined by the relation between the reading of 20 voltmeter 9 and that of ammeter I. In practice it has been found convenient to employ a slightly modified arrangement shown in Fig. 2. In this figure the ammeter is replaced by a constant resistance ll] of manganin wire or other metal or 25 alloy having negligible temperature coefiicient of resistance. The terminals of the constant resistance III are connected to the contacts H and I2 at one end of the double pole, double throw switch 13. Wires 3 and 3' are connected to contacts I 30 and I5 at other end of switch I 3. The center poles of switch l3 are connected to the terminals of a potentiometer I6. By means of switch I 3, the potentiometer l6 may be connected either to wires 3 and 3' or to terminals of constant resistance ill. 5 When potentiometer I6 is connected to wires 3 and 3, the potential difference of junctions 5 and 5 may be measured. When connected to terminals of constant resistance ID, the fall of potential through constant resistance l0 may be measured 4 by the same instrument. Since the fall of potential through resistance I0 is proportional to current flowing through the resistance, it follows that this fall of potential is a relative measure of the heating current flowing through heating e1e- 45 ment 2.

In use wire I is placed within the compartment where fluid velocity is to be ascertained as is also couple and solely supported thereby and being in mechanical and thermal contact but not in electrical contact with saidjunction, said thermocoucoil wrapped about one junction of said thermomeans for supplying electric energy to said heating element, means for adjusting the amoimt of heat supplied, means for measuring the amount of heat supplied and means for measuring the 5 B being Otherwise free'from al meeha electromotive force of the thermocouple. 5 ical' contact with any solid material, means for 3,"A device for measuring the velocity of flow measuring the electromotive force of the thermoof fluids comprising a thermocouple wholly imp means for Supplying electric energy mersed in the moving fluid, a heating coil wrapped the h a n coil, means r adjusting the energy about one junction of said thermocouple and solely pp d a d means for measuring the amount supported thereby and being in mechanical and 10 of energy supplied. thermal contact but not in electrical contact with 2. A device for measu t Velocity of o said junction, said thermocouple being otherwise o fluids o p s a thermocouple Wholly free from thermal or mechanical contact with mersed in t e m v fl a heating element any solid material, a source of direct current of wrapped as a coil about one junction of said therelectricity for applying energy to said heating coil, 15 mocouple d solely supported thereby and means for adjusting the amount of heating curing in mechanical and thermal contact but not i in electrical contact with said junction, said thering current and means for measuring the t mocouple being otherwise free from thermal or motive force of t thermocouple WILLIAM v. HUKILL.

mechanical contact with any solid material,

CERTIFICATE OF C ORRECTION.

itent No. 2,061,941.

WILLIAM) v. HUK-ILL It'is hereby certified that error appears in the printed specification of she above numbered patent requiring correction as follows: Page 2, second :olumn, line 16-, claim 3, strike out the syllable "cur-" and insert instead ;he words and syllable current, means for measuring the amount of heat-; and shat the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 16th day of February, 1937;

\ Henry Van Arsdale 3e'al) Acting Commissioner of Patents.

November 24, 1936. 

